1. Field of the Invention
The present invention relates to an ultra-wide frequency range ferrite-loaded constant impedance element, particularly, for presenting a constant terminal impedance in an extremely wide frequency range.
The present invention also relates to a constant phase difference circuit for deriving signal power, which is applied on an opening of a circuit arrangement having plural openings, for instance, a 3 dB directional coupler, from the circuit arrangement concerned with a predetermined phase difference from the signal appearing at the opening and concerned or another opening, particularly, to an ultra-wide frequency range constant phase circuit for obtaining an output signal maintaining a predetermined phase in an extremely wide frequency range.
2. Related Art Statement
In a conventional ferrite-loaded impedance element of this kind, a terminal impedance thereof is usually varied in response to a frequency variation in an operational range.
Accordingly, the conventional ferrite-loaded impedance element of this kind cannot be used for communication apparatus having extremely wide operational frequency ranges allotted for satellite communication, satellite broadcast, etc., in spite of the small size and the high efficiency thereof. Accordingly, there has been a need to develop an article having a constant impedance throughout a wide operational frequency range.
On the other hand, as for the constant phase circuit of this kind, a typical 3 dB directional coupler has been conventionally used. The directional coupler belongs to those of distributed coupling type as shown in FIG. 1A and of lumped constant type as shown in FIG. 1B, the former being provided with conjugated terminals, each consisting of ends of one fourth wave length parallel dual lines, while the latter being provided with conjugated terminals each consisting of connection points between two coils L and two capacitors C connected with both ends of the coils, so as to derive output signals having phases .phi.2 and .phi.3 which lag successively by 90 degrees behind the input signal phase .phi.1.
In contrast with the directional coupler thus formed of passive elements, another kind of conventional phase circuit is arranged by combining active elements as shown in FIG. 2, so as to obtain an output signal through a wide frequency range. In this phase circuit, a high frequency signal having a frequency f is applied to a frequency multiplier 2 from a signal source 1, so as to double the frequency f. The multiplied output signal of frequency 2f is divided into two branches, one of which is directly supplied to a frequency divider 3, while another of which is supplied to another frequency divider 5 through a 180 degree phase shifter 4, so as to divide the frequency 2f into one half and to derive two distributed output signals having the frequency f and the mutual phase difference of 90 degrees through filters 6 and 7 respectively.
However, all of the aforesaid conventional phase circuits have individual respective defects. Although the directional coupler can be extremely simply arranged, the amplitudes of two phase difference output signals having the phase difference .phi.2-.phi.3=90 degrees therebetween are further reduced, as shown in FIG. 1C, in response to the frequency difference from -3 dB at the respective central frequencies, which is determined by the line length of the distributed coupling type and which is an angular frequency .omega.=.sqroot.Lc of the lumped constant type, so that the directional coupler cannot be employed as a wide frequency range constant phase circuit.
On the other hand, the conventional constant phase circuit formed of active elements has a complicated arrangement as shown in FIG. 2, so that the constant phase circuit of this kind is not adapted for practical use.
Consequently, the removal of these defects is a subject of the conventional constant phase circuit to be solved.